The present invention relates to an air intake system for an internal combustion engine of a motor vehicle.
The air intake manifold of an internal combustion engine channels intake air from the engine's throttle body to the combustion chambers. A typical intake manifold, which can be mounted to a cylinder head of the engine, comprises a plenum and a plurality of runners that distribute airflow from the plenum to the intake ports of each cylinder. For a given air intake manifold, engine performance (e.g., the location of an engine's torque peak in the RPM band) is a function of the volume of the plenum, the cross-sectional area of the runners and, to a lesser extent, the length of the runners.
Conventional air intake manifolds have a fixed air flow geometry. With a fixed air flow geometry, the speed at which intake tuning occurs is also fixed, and the design of such air intake manifolds usually involves a compromise between achieving adequate torque at low speeds and sufficient horsepower at high speeds. In a tuned manifold, for example, the plenum volume, the length of the runners, and the cross-sectional area of the runners can be selected so that a pressure wave formed within the runners has a frequency that optimizes the pressure at each intake port when the corresponding intake valve is open.
One variable used to select the size and dimension of both the plenum and the runners is the engine volume (i.e., the engine displacement). For example, automobile engines can range in size from 2 liter, 4-cylinder models, to 6 liter or even larger 8-cylinder models. The total volume of an air intake manifold, which includes the volume of the plenum and the volume within the runners, is typically about twice the total engine displacement. Because the volume of an air intake manifold is proportional to the engine displacement, a different air intake manifold design is required for each engine size. This relationship results in a large number of different air intake manifold designs and the attendant expense associated with their design and manufacture.
Accordingly, it would be an advantage if a single air intake manifold design could be adapted to fit multiple engine sizes, thus reducing the required number of different air intake manifold designs.